A new method for the determination of methylparaben by ultra-performance liquid chromatography (UPLC) was developed. Methylparaben is often used as preservative, alone or in combination with other parabens, being added to cosmetic products, pharmaceutical products and foods to avoid microbial contamination. Due to its widespread use and potential risk to human health, assessing human exposure to this compound is of interest. A good determination and quantification of methylparaben was developed with a gradient elution using a mixture of methanol and water (60:40, v/v) within 1.455 min. Under optimized conditions, the linear working range extends over two orders of magnitude with relative standard deviations of intra- and inter-day precision below 2.3 %, and a detection limit of 0.02 ng μL-1 for methylparaben. The proposed method was successfully applied to the assay of methylparaben in cosmetic products with minimal sample preparation.

The simultaneous detection of L-ascorbic acid (AA) and acetaminophen (AC) at a boron-doped diamond electrode (BDDE), in a sodium sulphate supporting electrolyte, using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) was investigated. The calibration plots resulting from two distinct series of anodic current peaks versus concentration of AA and AC in single and di-component systems, obtained from CV and DPV data, presented linearity, with very good correlation coefficients. Fouling of the electrode surface was not evident and BDDE showed very reproducible voltammetric signals in all investigated situations. The relative standard deviations of 2 -3 %, high sensitivity values, and low limits of detection evaluated from DPV data in single systems, have been practically recovered in di-component standard and real sample solutions. The anodic assessment with the use of DPV was additionally verified by the simultaneous determination of AA and AC in real samples prepared from pharmaceutical products. Using a very simple supporting electrolyte, neutral unbuffered sodium sulphate solution, the DPV at a BDDE was confirmed as an easily applicable electroanalytical option. Individual and average values corresponding to AA and AC content in an investigated pharmaceutical product were determined by DPV coupled with standard addition method giving results in good accordance with the composition indicated by the supplier.

A boron-doped diamond electrode (BDDE) was used for the simultaneous anodic determination Of L-ascorbic acid (AA) and acetaminophen (AC) in aqueous buffered media by differential pulse voltammetry (DPV). Linear calibration plots of anodic current peaks versus concentration were obtained for both analytes in the concentration range 0.01 - 0.1 mM with very high correlation coefficients. RSD of 2 - 3% and high sensitivities were obtained from DPV data in single and dicomponent systems. The potential applicability of the DPV technique associated with standard addition was illustrated by simultaneous determination of AA and AC in real sample solutions made up from pharmaceutical products.

In this paper, the electrochemical behaviour of several parabens preservatives, i.e. esters of p-hydroxybenzoic acid, methyl-, ethyl- and propyl-4-hydroxybenzoates as methyl-, ethyl- and propyl-parabens (MB, EB, and PB), has been investigated at a commercial boron-doped diamond electrode (BDDE), especially in the anodic potential range, in both hydro-alcoholic and aqueous media. The cyclic voltammetric and chronoamperometric measurements yielded calibration plots with very good linearity (R2 between 0.990 and 0.998) and high sensitivity, useful for detection and analytical applications. The determination of the characteristics of individual compounds, of an “overall paraben index”, the assessment of the stability and the saturation solubility in water, and the amperometric sensing and determination in double distilled, tap and river water matrix of the relatively slightly soluble investigated parabens have been carried out using electrochemical alternative. Estimated water solubility was correlated with the octanol-water partition coefficient. Several ideas regarding stability and persistence of the presumptive eco-toxic investigated preservatives in the environment or water systems have been adjacently discussed.

TAA is a harmful, presumptive pollutant in tap waters and waste waters. Several alternatives have been tested as new possibilities for the anodic determination of TAA in aqueous solutions, simulated waste waters and tap water. The electrochemical behaviour of thioacetamide ( TAA) was investigated at a boron-doped diamond (BDD) electrode both in unbuffered 0.1 M Na2SO4 and buffered solutions as supporting electrolytes. The anodic oxidation of TAA showed well-defined limiting currents or current peaks and a good linearity of the amperometric signal vs. concentration plots. The analytical parameters of sensitivity, RSD and LOD, obtained under various experimental conditions, suggest the suitability of the BDD electrode for electroanalytical purposes. Low fouling effects, good reproducibility and stability, as well as the sharpness of the amperometric signals in both unbuffered/buffered acidic or neutral media, highly superior to those obtained using a glassy carbon ( GC) electrode, recommend the unmodified BDD electrode as a promising potential amperometric sensor for environmental applications, regarding the direct anodic determination of TAA in aqueous media.